In some cases, on a road surface at an entrance portion of a building or an underground space, a floating flap gate that is configured to block said entrance portion is installed in order to prevent, at the time of rising water, the rising water from flowing into the building or the underground space.
The floating flap gate of this type has a configuration in which the gate leaf is provided with a buoyancy forming portion, and by using water pressure of water flowing into the entrance portion of the building or the underground space and buoyancy of the gate leaf itself, the gate leaf is raised to block said entrance portion.
The gate leaf of the floating flap gate is installed on the road surface or a receiving base provided on the road surface so as to be freely rotatable via a hinge provided at each of two locations on the gate leaf in a width direction thereof (see, for example, Patent Literature 1).
In a case, however, where the gate leaf is structured to be raised via the hinge, such a complicated structure requires higher levels of manufacturing precision and assembly precision, resulting in an increase in manufacturing man-hour. Furthermore, a load acting on the gate leaf is concentrated on the hinge, thus requiring a frame that is a component of the gate leaf to have high strength.